It's not the type of mudfest where candidates call each other names. Rather, it's a campaign where surrogates attack the candidates from the shadows, with innuendo and sleaze. It's all done via whispering campaigns. In the decisive 2000 GOP primary contest between "W" and McCain, Republicans started using their tactics on each other, and 2008 is no exception.
South Carolina is also the first contest where four of the five major GOP candidates are all putting up a fight, with only Giuliani sitting it out. (Romney's not conceding the state, but he's concentrating a bit more on Nevada, which the media will somehow try to ignore.)
In polls of SC voters taken after Iowa, Huckabee had the lead; then, in polls since New Hampshire, McCain took the lead. There's only one poll out now that is entirely after Romney's Michigan victory, from Rasmussen, and it has McCain and Huckabee tied, with Romney and Thompson not too far behind, and a lot of voters still undecided or likely to change their minds.
Giuliani may regret not contesting SC--it's pretty clear that McCain has benefitted from Rudy's decline in the state, picking up voters from among the state's large veterans populations for whom national security is the biggest concern. If McCain wins and leverages his momentum into Florida, Giuliani can blame his silly strategy of disappearing from view during the most critical month of the campaign.